1. Field of the Invention
This invention relates generally to a mechanism for splicing one continuous web of paper or like material, which is being fed into a printing press or like machine by being paid out from its roll, to a new roll of such web as the old roll is nearly used up. More specifically, the invention deals with a system to be incorporated with such web splicer mechanism for automatically driving the new web roll at a peripheral speed matching the running speed of the old web, preparatory to the splicing of the old web to the new roll.
2. Description of the Prior Art
In a web-fed printing press for newspaper production, for instance, the web of paper being printed upon by being unwound from its roll is automatically spliced to a new web roll, which is in rotation with a peripheral speed matching the running speed of the old web, as the old web roll is consumed to a predefined diameter, in a manner causing no interruption in printing. A successful splicing of the webs depends to a large measure upon the matching of the peripheral speed of the new web roll to the running speed of the old web. A variety of suggestions have indeed been made toward this end.
Typical of such known suggestions, and perhaps bearing the closest resemblance to the instant invention, is Japanese Unexamined Patent Publication No. 1-150661. It teaches to sense the peripheral speed of the new web roll photoelectrically, by means comprising a laser and an associated photoreceptor, as the roll is set into rotation in a predetermined splicing position immediately downstream of the old web roll being consumed. The photoelectrically detected peripheral speed of the new web roll is compared, by associated control electronics, with the running speed of the old web. The drive motor of the new web roll has its speed controlled according to the departure of the peripheral speed of the new web roll from the traveling speed of the old web, in order to match the two speeds and hence to splice the old web to the new web roll without a break in printing.
This prior art system has some ambiguities and obvious shortcomings. The two web rolls to be spliced together are both mounted to a rotary roll stand comprising one pair of carrier arms rotatably carrying one web roll, and another such pair rotatably carrying the other web roll. The two pairs of carrier arms are both mounted to a rotary shaft and extend in diametrically opposite directions therefrom. As the old web roll is consumed to a predetermined diameter, the two carrier arm pairs are jointly turned through an angle required to bring the new web roll to a splicing position spaced a preassigned distance from the old web being fed into the press by being paid out from the old web roll.
The trouble is that new web rolls come in several different diameters, not in one. According to the current standards the minimum diameter of unused web rolls is only six tenths of the maximum. When the roll stand is turned through a required angle as above, the new web roll of any given diameter can be positioned at the prescribed spacing from the old web traveling along its predefined path. This, however, does not mean that new web rolls of varying diameters occupy the same position with respect to the old web. Their axes will be in different positions depending upon their diameters.
In photoelectrically sensing the rotational speed of the new web roll, as suggested by the prior art, it is essential that both light source and photoreceptor be positioned at prescribed spacings from, and at prescribed angles to, the new web roll; otherwise, the peripheral speed of the roll would be either undetectable or not accurately detectable. The Japanese patent application cited above discloses no means whatsoever for correctly positioning the photoelectric sensor means with respect to the new web rolls of varying diameters. This prior art apparatus can detect the peripheral speed of the new web roll having a prescribed diameter only, or a diameter in a narrowly limited range of diameters only.
The cited Japanese patent application teaches to compare the peripheral speeds of the old and the new web roll for matching them, suggesting use of a pulse generator for detecting the peripheral speed of the old web roll. The peripheral speed of the old web roll is said to be detectable by multiplying the angular velocity of the old web roll by its diameter. The application is, however, silent on where the pulse generator is positioned, how the angular velocity of the old web roll is ascertained by the pulse generator, and how the roll diameter, which is incessantly diminishing, is determined.
The present invention has it as a general object to splice successive rolls of paper web or the like without any such trouble as web breakage or misprinting and hence to drastically improve the efficiency of printing through reduction of downtime due to such causes.
A more specific object of the invention is to make it possible to position the photoelectric speed sensor in the correct sensing position relative to the new web roll being held in the splicing position, regardless of its diameter or, to be more exact, no matter which of the standardized diameters it may have.
Briefly, the present invention concerns, in an apparatus for splicing a web of paper or like material, which is traveling at any given speed along a predefined path by being unwound from an old web roll, to a new web roll of a variable diameter being rotated in a splicing position in which the new web roll of any diameter is spaced a prescribed constant distance from the web traveling along the predefined path, a speed matching system for matching the peripheral speed of the new web roll to the running speed of the old web traveling along the predefined path preparatory to the splicing of the webs.
More specifically, the web speed matching system according to the invention comprises a first speed sensor for sensing the running speed of the web traveling along the predefined path by being unwound from the old web roll, and a second speed sensor for photoelectrically sensing the peripheral speed of the new web roll being driven in the splicing position. For optimally positioning the second speed sensor relative to the new web roll of a variable diameter being held in the splicing position, there is provided a sensor positioning mechanism capable of moving the second speed sensor along two orthogonal axes which are determined in relation to the axis of rotation of the new web roll. An electric control circuit is provided which has inputs connected respectively to the first and the second speed sensor, and an output connected to the drive means for the new web roll, in order to cause the latter to be controllably energized according to the possible departure of the peripheral speed of the new web roll, in rotation in the splicing position, from the running speed of the old web traveling along the predefined path.
Thus, whatever the diameter of the new web roll may be, within, of course, reasonable limits, the second speed sensor can be optimally positioned for correct measurement of its peripheral speed. A correct measurement of the peripheral speed of the new web roll leads to correct determination of its departure from the running speed of the old web, and hence to correct energization of the new web roll drive motor for matching the new web roll peripheral speed to the traveling speed of the old web.
In the preferred embodiment to be disclosed subsequently, the sensor positioning mechanism comprises first drive means for reciprocably moving the second speed sensor in a first direction at right angles with the axis of the new web roll, second drive means for reciprocably moving the second speed sensor in a second direction at right angles with the first direction and with the axis of the new web roll, and a sensor positioning control circuit electrically connected to the first and the second drive means for controlling the same.
The new web roll is rotatably mounted to a rotary web roll stand which is angularly displaceable to carry the new web roll from a standby position to the splicing position. Therefore, in the preferred embodiment, a displacement sensor is provided for sensing the angle of displacement of the web roll stand in moving the new web roll from the standby position to the splicing position. The sensor positioning control circuit is electrically connected to the displacement sensor for ascertaining the position of the axis of the new web roll in the first direction on the basis of the angle of displacement of the web roll stand and for causing the first drive means to bring the second speed sensor to a preselected position in the first direction.
The preferred embodiment also includes a web roll distance sensor for sensing its own distance from the surface of the new web roll, the distance sensor being supported in fixed positional relationship to the second speed sensor for joint movement therewith. The sensor positioning control circuit is electrically connected not only to the web roll stand displacement sensor but to the web roll distance sensor as well. Receiving outputs from these sensors, the sensor positioning control circuit is enabled to automatically readjust the position of the second speed sensor for most accurate determination of the peripheral speed of each new web roll as the latter is carried to the splicing position and set into rotation for splicing.
The above and other objects, features and advantages of this invention will become more apparent, and the invention itself will best be understood, from a study of the following description and appended claims, with reference had to the attached drawings showing the preferred embodiment of the invention.